The K7RA Solar Update

SEATTLE, WA, Apr 22, 2005--Little changed in terms of sunspots and solar flux this week, but it was one of those periods were average daily sunspot numbers were up slightly and average daily solar flux was down a little. Average daily sunspot numbers were up more than 10 points to 50.9, and average daily solar flux was down 5 points to 81.9.

Geomagnetic conditions were calmer and quieter, with no really stormy days at all. As for the most unsettled days, the planetary A index was 19 on April 14, while the mid-latitude A index was 14. On April 20, the planetary A index was 21, and the mid-latitude A index was 12.

No large sunspots are detected on the sun's far side, and the projection for the next week is for more of the same in terms of solar flux and sunspot numbers. April 25-28 could see a slight rise in sunspot count. April 22-23 could produce some unsettled geomagnetic conditions if the interplanetary magnetic field turns south. Currently, the field points north, tending to deflect any solar wind. While there isn't much in the way of sunspots, at least conditions are quiet and there is more sunlight for those of us in the Northern Hemisphere.

Randy Crews, W7TJ, of Spokane, Washington, wrote to recommend the article "The 160-Meter Band: An Enigma Shrouded in Mystery," by Cary Oler and Dr Theodore J. Cohen, N4XX. It originally appeared in the March and April 1998 editions of CQ. Crews says it's one of the best articles on 160-meter propagation he's ever read.

For more information concerning radio propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page.

Sunspot numbers for April 14 through 20 were 63, 61, 52, 54, 44, 43 and 39, with a mean of 50.9. The 10.7 cm flux was 85.4, 84.9, 82.9, 83.6, 81.3, 78.2 and 77, with a mean of 81.9. Estimated planetary A indices were 19, 13, 7, 5, 8, 8 and 21, with a mean of 11.6. Estimated mid-latitude A indices were 14, 7, 4, 4, 5, 6 and 12, with a mean of 7.4.

Amateur solar observer Tad Cook, K7RA, Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears in The ARRL Letter. Readers may contact the author via e-mail.

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